Zeta potential (ζ) is a key indicator of the stability of colloidal dispersions. The higher the magnitude of the zeta potential (that is, highly positive OR highly negative), the more stable the colloid. A lower-magnitude zeta potential indicates a less stable colloid; in other words, a tendency towards aggregation or coagulation. Thus, knowledge of zeta potential is important for optimizing processes and for quality control, especially in industries such as pharmaceutical, food and beverages, chemicals, and more.
Frequently, the zeta potential of particles and macromolecules in solution is determined by electrophoretic light scattering (ELS), which is also called laser Doppler electrophoresis. It measures the speed of the particles (= electrophoretic mobility, µ) within a defined electric field. The magnitude of the zeta potential indicates the degree of electrostatic repulsion between particles in dispersion. Each particle in solution exhibits a zeta potential due to its surface charge. Zeta potential, however, cannot be measured directly; therefore it must be calculated from the electrophoretic mobility (µ), which can be measured directly.